The present invention relates to rolls for use in calenders and the like. More particularly, the invention relates to improvements in assemblies which include one or more rolls and can be used to treat running webs of textile material, paper, metallic foil, plastic foil or the like. Still more particularly, the invention relates to improvements in assemblies wherein at least one roll is constructed and assembled in such a way that the configuration of its peripheral surface can be changed so as to allow for the application of adequate pressure against any selected portion of the running web, as seen in the longitudinal direction of the nip through which the web is caused to advance.
It is well known to construct an adjustable or deformable roll for use in a calender or the like in such a way that the roll comprises a deformable hollow cylindrical shell which surrounds a stationary carrier. A hydrostatic bearing unit is installed between the carrier and the shell and serves to urge selected portions of the shell against the adjacent portion of the running web with a predetermined force. It is also known to mount the shell on two bearings which are disposed at the ends of the carrier and include annular bearing members movable relative to the carrier in the radial direction of the shell. As a rule, the bearing members are held against rotation relative to the carrier.
A roll of the above outlined character is disclosed in German Pat. No. 28 26 316. It is mounted at a level above a second roll and defines therewith an elongated nip for the passage of the running web. The hydrostatic bearing unit comprises a plurality of hydrostatic bearing elements which can act against the internal surface of the shell, and one or more pressure generating or biasing devices which urge the bearing elements downwardly and away from the carrier. The internal surfaces of the two bearing members are acted upon by pistons which tend to lift the shell against the action of gravity and in a direction away from the second roll.
A different roll is disclosed in German Pat. No. 31 38 365. In the assembly which is described in this patent, the shell is disposed below the second roll and the annular bearing members are acted upon by pistons serving to take up the weight of the shell as well as of any other parts which share the movements of the shell. This exhibits the advantage that the weight of the shell and the weight of any parts which are movable therewith need not be taken into consideration during selection of pressures which are applied by way of the hydrostatic bearing unit so as to regulate the pressure in the nip. In each of the aforedescribed conventional rolls, the space within the central portion of the shell communicates with the spaces within the annular bearing members.
The patented proposals exhibit the drawback that the pistons which act upon the bearing members are highly likely to cause a pronounced deformation of bearing members and of antifriction bearings which are associated with such bearing members. This applies especially when the roll is designed to take up and transmit substantial forces.